1. Field of the Invention
The present invention relates to semiconductor devices in which semiconductor sensor chips such as microphone chips and pressure sensor chips are arranged inside of hollow cavities.
This application claims priority on Japanese Patent Application No. 2007-36294, the content of which is incorporated herein by reference.
2. Description of the Related Art
Conventionally-known semiconductor devices, examples of which are disclosed in U.S. Pat. No. 6,781,231 and Japanese Patent Application Publication No. 2004-537182, are each designed such that a substrate having a chip mount surface for mounting a semiconductor sensor chip for detecting pressure variations such as variations of sound pressures is covered with a cover member, so that the semiconductor sensor chip is arranged inside of a hollow cavity defined by the substrate and the cover member. The cover member has an opening allowing the cavity to communicate with external space; hence, pressure variations occurring in external space are transmitted to the semiconductor sensor chip via the opening of the cover member. The opening of the cover member is positioned opposite to the semiconductor sensor chip and is normally formed in a circular shape.
When the opening of the cover member is positioned opposite to the semiconductor sensor chip arranged inside of the cavity of the semiconductor device, the semiconductor sensor chip must be directly exposed to the external space via the opening and is thus easily affected by environmental factors such as sunlight and dust.
Normally, a single opening, which is formed in a circular shape in plan view, is formed at a prescribed position of the cover member, which is directly opposite to a diaphragm of the semiconductor sensor chip. In order to adequately introduce pressure variations into the cavity of the semiconductor device, it is necessary to sufficiently increase the opening area; however, when the opening area is increased, negative influences (or negative effects) due to environmental factors will be correspondingly increased. When the opening is formed in a circular shape, a drawback may likely occur such that small foreign matters smaller than the diameter of the opening may be easily introduced into the cavity of the semiconductor device.
In order to protect semiconductor sensor chips from negative influences due to environmental factors, some conventionally-known semiconductor devices are equipped with environmental barriers for avoiding infiltration of environmental factors. However, environmental barriers make it complex to produce semiconductor devices in manufacturing.